jQuey之Callbacks、Deferred實現

做者：zhangl
原文：jQuey之Callbacks實現

jQuery.myCallbacks = function () {
    // 這裏主要是options參數爲'once；memory；once memory'
    // 獲取options
    var options = arguments[0] || '';
    // 蒐集fire被調用時，傳入的參數
    var arg = [];
    // 蒐集add傳入的函數
    var list = [];
    // 判斷cb是否調用過fire
    var isFired = false;
    // 當前fire調用的函數索引
    var fireIndex = 0;
    
    function fire() {
        // 循環執行add添加的函數
        for (; fireIndex < list.length; fireIndex++) {
            list[fireIndex].apply(window, arg);
        }
        // 若是options是once，清空list數組
        if (options.indexOf('once') !== -1) {
            list.length = 0;
            fireIndex = 0;
        }
    }
    
    return {
        add: function (func) {
            list.push(func);
            // options爲memory而且fire被調用用過
            if (options.indexOf('memory') !== -1 && isFired) {
                fire();
            }
            return this;
        },
        fire: function () {
            arg = arguments;
            isFired = true;
            fireIndex = 0;
            fire();
        }
    };
};
複製代碼

jQuery.myDeferred = function () {
    var arrCallbacks = [
        [jQuery.Callbacks('once memory'), 'done', 'resolve'],
        [jQuery.Callbacks('once memory'), 'fail', 'reject'],
        [jQuery.Callbacks('memory'), 'progress', 'notify']
    ];
    var deferred = {};
    // 是不是pending狀態
    var isPending = true;
    for (var i = 0; i < arrCallbacks.length; i++) {
        // deferred綁定done, fial, progress API
        deferred[arrCallbacks[i][1]] = (function (index) {
            return function (func) {
                arrCallbacks[i][0].add(func);
            }
        })(i);
        // deferred綁定resolve, reject, notify API
        deferred[arrCallbacks[i][2]] = (function (index) {
            return function () {
                if (isPending) {
                    arrCallbacks[i][0].fire.apply(window, arguments);
                    arrCallbacks[i][2] === 'resolve' || arrCallbacks[i][2] === 'reject' ? isPending = false : '';
                }
            }
        })(i);
    }
    
    return deferred;
};
複製代碼